1. Field of the Invention
The present invention relates to a manufacturing method for a semiconductor device and a semiconductor manufacturing apparatus, and more particularly, to a semiconductor device manufacturing method utilizing a CVD (Chemical Vapor Deposition) film formation process and a semiconductor manufacturing apparatus utilizing a CVD film formation process.
2. Description of the Related Art
In a processing for manufacturing a semiconductor device, a film is formed on a substrate to be processed such as a semiconductor silicon wafer by a chemical vapor deposition (CVD) method.
A wafer processing will be explained below with reference to FIGS. 3 and 4.
In a state where a load lock chamber 1 and a reaction furnace 2 are under the atmospheric pressure, a boat 10 is lowered (unloaded) from the reaction furnace 2 to the load lock chamber 1. In the state where the boat 10 is lowered, a predetermined number of wafers 11 are mounted on the boat 10 by a substrate transfer apparatus (not shown) (step 41).
A temperature in the reaction furnace 2 is maintained at a film forming temperature during operation. The boat 10 is hoisted by a boat elevator (not shown), and the wafers 11 are brought (loaded) into the reaction furnace 2 (step 42).
An interior of the reaction furnace 2 is evacuated into vacuum by an evacuating device 9 (step 43), reaction gas is introduced into the reaction furnace 2 through gas introducing lines 7 and 8, and films are formed on the wafers 11 (step 44).
After the film forming processing is completed, the pressure in the reaction furnace 2 is brought back to the atmospheric pressure (step 45), and the boat 10 is unloaded and pulled into the load lock chamber 1 by the boat elevator (not shown) (step 46). In the load lock chamber 1, the boat 10 is cooled (step 47), the wafers 11 are removed by the substrate transfer apparatus (not shown) (step 48).
When the wafer removal is completed, unprocessed wafers are further mounted on the boat 10 and then, the load lock chamber 1 is once evacuated into vacuum by a vacuum evacuating device 13 to eliminate moisture and oxygen in the air. Thereafter, nitrogen gas is introduced from a gas purge nozzle 12, the pressure in the load lock chamber 1 is brought back to the atmospheric pressure which is substantially the same as the pressure in the reaction furnace 2. Next, the boat 10 is loaded into the reaction furnace 2, and the processing is continued.
If a film, e.g. an SiN film is formed on a substrate to be processed such as a wafer and a glass substrate by a CVD apparatus, by-products of reaction are adhered and deposited on a wall surface of the reaction furnace, thereby forming the film. This deposited film grows whenever the substrate processing is repeated, and when a thickness of the film reaches a predetermined value, cracking and peeling are caused to generate particles. The particles float in the reaction furnace and adhere to the substrate to be processed. When the number of particles is increased and the number of particles adhering to the substrate to be processed is increased, detrimental effects that yield is lowered and quality of product is deteriorated are generated. Especially in the case of a Si3N4 film whose film thickness generated by one time processing is equal to or greater than 1000 xc3x85, this phenomenon becomes remarkable. It is conceivable that the Si3N4 film is subjected to a self cleaning which is usually carried out in the case of polycrystalline film. However, in the case of the Si3N4 film, since particles are generated when the deposited film thickness reaches 1 xcexcm, it is necessary to carry out the cleaning whenever film thickness of the deposited Si3N4 film reaches 1 xcexcm. Therefore, a frequency of the cleaning is higher than that of the polycrystalline film, and this causes inconvenience that quartz member is degraded due to the cleaning gas.
It is considered that the cracking of the reaction by-product deposited film is generated if residue stress at the time of deposited film formation is increased together with growth of the film, and thermal stress is generated due to difference in thermal expansion between the deposited film and an outer tube 5 and between the deposited film and an inner tube 6, and these stresses exceed tolerance limits (mechanical disruptive strength of the deposited film). The cracking of the deposited film progresses into film peeling in due time, but particles are generated even when the deposited film cracking is generated. The particle at that time is extremely fine as small as about 0.1 to 0.2 xcexcm.
Further, it is considered that the cracking of the deposited film is generated during a semiconductor manufacturing process. When the thickness of the deposited film reaches about 1 xcexcm, the number of particles adhering to a wafer becomes 100/wafer or greater, and the number of the particles is never reduced thereafter.
For this reason, it is necessary to eliminate the deposited film in order to maintain the number of particle adhering to a wafer at a level equal to or lower than a predetermined value, and the inner tube 6 and the outer tube 5 constituting the reaction furnace 2 was cleaned before the thickness of the deposited film reaches about 1 xcexcm.
When constituent members of the reaction furnace 2 such as the outer tube 5 and the inner tube 6 are cleaned, operation of the semiconductor manufacturing apparatus is stopped and the reaction furnace 2 is disassembled. Therefore, if the cleaning frequency is high, there are problems that the rate of operation of the semiconductor manufacturing apparatus is lowered, and productivity is deteriorated.
The present inventor has found that it is possible to reduce adhesion of the fine particles to a wafer by forcibly generating a cracking in a deposited film of reaction by-products during the manufacturing process of a semiconductor apparatus, and by forcibly discharging out, by means of a gas purge, the fine particles generated when the cracking was generated, and as a result, it is possible to reduce the frequency of cleaning operations of a reaction furnace, and to enhance the productivity.
The present inventor has found that it is possible to reduce adhesion of the fine particles to a wafer by lowering the temperature in a reaction furnace, in a state where there are no substrates to be processed in the reaction furnace, to increase the stress of a reaction by-product deposited film adhered to the reaction furnace, and by forcibly generating a cracking in the deposited film, and by forcibly discharging out, by means of a gas purge, the fine particles generated when the cracking was generated.
The present invention is based upon the above-mentioned findings, and according to a first aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
forming a film on a substrate to be processed in a reaction furnace at a first temperature,
unloading the substrate from the reaction furnace, and
lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature, and conducting a gas purge, using only an inert gas, in the reaction furnace after the substrate has been unloaded from the reaction furnace.
According to a second aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
conducting batch processing in a reaction furnace in a state in which a plurality of substrates to be processed are mounted on a boat, to form films on the plurality of substrates to be processed at a first temperature,
thereafter unloading the boat from the reaction furnace,
taking out processed substrates,
after the boat has been unloaded from the reaction furnace, lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature, conducting a gas purge in the reaction furnace using only an inert gas, and thereafter raising the temperature in the reaction furnace to a temperature higher than the second temperature,
mounting, on the boat, a plurality of substrates to be processed next, and
loading, into the reaction furnace, the boat on which the plurality of substrates to be processed next are mounted, after raising a temperature in the reaction furnace to the temperature higher than the second temperature.
According to a third aspect of the present invention, there is provided a semiconductor manufacturing apparatus, comprising:
a reaction furnace for subjecting a substrate or substrates to be processed to film forming processing,
a reaction gas introducing member for introducing a reaction gas into the reaction furnace,
an evacuating device for evacuating the reaction furnace,
an inert gas introducing member for introducing an inert gas into the reaction furnace, and
a temperature controller for controlling a temperature in the reaction furnace, wherein
the temperature controller controls a temperature in the reaction furnace to a first temperature and the reaction gas introducing member introduces the reaction gas into the reaction furnace subjecting the substrate or the substrates to be processed to the film forming processing and
after a processed substrate or substrates have been unloaded from the reaction furnace, the temperature controller drops a temperature in the reaction furnace to a second temperature which is lower than the first temperature and a gas purge is conducted in the reaction furnace using only the inert gas by introducing the inert gas into the reaction furnace by the inert gas introducing member and evacuating the reaction furnace by the evacuating device.
According to a fourth aspect of the present invention, there is provided a method for forming a film, comprising:
forming a film on a substrate to be processed in a reaction furnace at a first temperature,
unloading the substrate from the reaction furnace, and
lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature, and conducting a gas purge, using only an inert gas, in the reaction furnace in a state in which the substrate is unloaded from the reaction furnace.
According to a fifth aspect of the present invention, there is provided a film forming apparatus, comprising:
a reaction furnace for subjecting a substrate or substrates to be processed to film forming processing,
a reaction gas introducing member for introducing a reaction gas into the reaction furnace,
an evacuating device for evacuating the reaction furnace,
an inert gas introducing member for introducing an inert gas into the reaction furnace, and
a temperature controller for controlling a temperature in the reaction furnace, wherein
the temperature controller controls the temperature in the reaction furnace to a first temperature and the reaction gas introducing member introduces the reaction gas into the reaction furnace subjecting the substrate or the substrates to be processed to the film forming processing and
after a processed substrate or substrates have been unloaded from the reaction furnace, the temperature controller drops the temperature in the reaction furnace to a second temperature which is lower than the first temperature and a gas purge is conducted in the reaction furnace using only the inert gas by introducing the inert gas into the reaction furnace by the inert gas introducing member and evacuating the reaction furnace by the evacuating device.
According to a sixth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
heating an inside of a reaction chamber with a heater disposed outside of the reaction chamber to a first temperature,
forming a film on a substrate to be processed in the reaction chamber at the first temperature,
unloading the substrate from the reaction chamber, and
lowering a temperature in the reaction chamber using only an inert gas to a second temperature which is lower than the first temperature, and
conducting a gas purge in the reaction chamber after the substrate has been unloaded from the reaction chamber.
According to a seventh aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
heating an inside of a reaction chamber with a heater disposed outside of the reaction chamber to a first temperature,
conducting batch processing in the reaction chamber when a plurality of substrates to be processed are mounted on a boat, to form films on the plurality of substrates to be processed at the first temperature,
thereafter, unloading the boat from the reaction chamber,
taking out processed substrates,
after the boat has been unloaded from the reaction chamber, lowering a temperature in the reaction chamber to a second temperature which is lower than the first temperature, conducting a gas purge in the reaction chamber using only an inert gas, and thereafter raising the temperature in the reaction chamber to a temperature higher than the second temperature,
mounting, on the boat, a plurality of substrates to be processed next, and
loading, into the reaction chamber, the boat on which the plurality of substrates to be processed next are mounted, after raising the temperature in the reaction chamber to the temperature higher than the second temperature.
According to an eighth aspect of the present invention, there is provided a semiconductor manufacturing apparatus comprising:
a reaction chamber for subjecting a substrate or substrates to be processed to film forming processing,
a heater disposed outside of the reaction chamber for heating an inside of the reaction chamber,
a reaction gas introducing member for introducing a reaction gas into the reaction chamber,
an evacuating device for evacuating the reaction chamber,
an inert gas introducing member for introducing an inert gas into the reaction chamber, and
a temperature controller for controlling a temperature in the reaction chamber, wherein
the temperature controller controls the temperature in the reaction chamber to a first temperature and the reaction gas introducing member introduces the reaction gas into the reaction chamber subjecting the substrate or the substrates to be processed to the film forming processing and
after a processed substrate or substrates have been unloaded from the reaction chamber, the temperature controller drops the temperature in the reaction chamber to a second temperature which is lower than the first temperature and a gas purge, using only the inert gas, is conducted in the reaction chamber by introducing the inert gas into the reaction chamber by the inert gas introducing member and evacuating the reaction chamber by the evacuating device.
According to a ninth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising:
forming a film on a substrate to be processed in a reaction furnace at a first temperature;
unloading the substrate from the reaction furnace;
after the substrate is unloaded from the reaction furnace, lowering a temperature in the reaction furnace to a second temperature which is lower than the first temperature and conducting a gas purge in the reaction furnace; and
after lowering the temperature in the reaction furnace and conducting the gas purge, loading a substrate to be processed next into the reaction furnace, wherein
a range of temperature drop in the temperature lowering from the first temperature to the second temperature is greater than a range of temperature drop generated in the reaction furnace when the substrate to be processed next is loaded into the reaction furnace.